This invention is related to a flow control valve in which a piston head moves in a valve chamber to a position depending upon the differential pressure across a fixed orifice. The fixed orifice is defined by an annular opening between the edge of the piston head and the cylindrical wall of the valve chamber.
Flow control valves are known in the prior art. See for example, U.S. Pat. No. 4,922,956 which was issued May 8, 1990 to Frank A. Taube Sr., and Edward J. Rozniecki for "Fluid Flow Control Regulator"; U.S. Pat. No. 4,237,922 which was issued Dec. 9, 1980, to Albin Maier for "in-Line Flow Control Valve"; U.S. Pat. No. 4,175,584 which was issued Nov. 27, 1979, to Sotokazu Rikuta for "Control Valve for Keeping the Rate of Flow at a Fixed Value"; and U.S. Pat. No. 3,752,182 which was issued Aug. 14, 1973, to Glen Brand for "Pressure Compensated Flow Control Valve".
Such flow control valves permit the flow of only one fluid medium through the unit. Further such units typically require complex upstream pressure signal passages from the high pressure side of a measuring orifice, and have several moving components.